The head of the Metropolitan Police has suggested there could be more drugs tests for employees at work, as part of attempts to discourage recreational users.

Bernard Hogan-Howe made the suggestion as part of a wide ranging speech at the think-tank Policy Exchange in London on Tuesday night, where he said idea might be useful "if you are trying to affect the demand side of things." But Hogan-Howe said the aim would be to act as a deterrent, not to inform the police.

"How many drug addicts have you got working for you?" he asked the audience. "I'd argue none of us know. But I wouldn't want to be operated on by one, nor have one drive a bus. Some organisations have some very risky operations that you do not want people with cravings doing, running your computers.

"Someone who's affected by cannabis use, cannabis that stays in the system for about 28 days. Cannabis that's now a far higher potency than the stuff of the 60s."

Admitting it needed a "sophisticated discussion", the Met police commissioner said: "If you want to do something about demand, we really need to be absolute in our terms that we want to do something about it. Where do people think these millions of pounds come from?

"Cocaine use, for example, the money's coming from people who are employed, a significant amount is coming from people who hold a job down.

"My point is, what can you do to start testing in employment, not to tell the police, but as an issue of employment. You say, 'You've got a choice; you either change what you're doing, because I don't want you working for me anymore.'"

Hogan-Howe said the tests could be carried out on teachers and nurses, but suggested the practice could extend into the private sector. "I think at least you've got to think about that, rather than thinking about the other extreme which is legalisation."

Drugs testing by employers is common practice in major American firms but is not routine in Britain, except for those working in highly sensitive jobs like the security and intelligence services.

Hogan-Howe made the suggestions as part of a speech where he outlined his approach to reforming policing in London, a project he referred to as "total policing" -where he sees the public having a much better and more engaged relationship with the Met.

He also sees technology playing a greater role in detecting crime and fully supports the government's Communications Bill - a controversial law which many fear will lead to greater powers for the state to snoop on people.

Unlike every other force in England and Wales London's police budget has not seen cuts this year, because of pressures including the Olympics and the Diamond Jubilee. But from 2013 London's policing budget will be cut by up to half a billion pounds - or 14%.

Hogan-Howe told the audience that during that period protests against austerity would increase and be likely to take place in central London, forcing the Met to bring police from outer boroughs into the centre. "Finding the balance will be a difficult challenge." he said.

But he said that the Met's technology was in many ways out-of-date; pledging that investment in new kit would be his priority.

"If we ended up with less people but better technology, and ended up being better at fighting crime, I'd say that wouldn't be a bad thing," he said, suggesting that the police could tap into the Automatic Number Plate Recognition systems used in petrol stations, cross-matching the data with their own databases.

On the government's Bill to allow access to new forms of private data, Hogan-Howe insisted that the plans in no way further encroached on civil liberties than existing laws; they merely brought the powers of the state into line with emerging technologies, he insisted.

"The change is entirely to do with a change in technology rather than any new intrusion. It's the same level of intrusion, it's just a different way of doing it," he claimed. "I'd rather have the benefits with same restraints to protect people's rights than not have the benefit at all.

"Lives will be lost without that sort of information," he added.

Turning to the Olympics, he said there remained no specific threat to the games, but warned that the focus on the Olympics site in east London missed the point that terrorists could attack another site in London away from Stratford - "And that would still be seen as an attack on the Olympics," he said.